The use of internal combustion engines (hereinafter abbreviated as ICE) has dominated the automotive industry over the last century. However, environmental concerns, dependence on oil, restrictions enforced by governments, and an enormous demand for improved fuel economy has encouraged automotive manufacturers to develop more fuel-efficient and environmentally friendly solutions. Alternative powertrains, meaning that alternative power sources to the ICE are employed to propel a vehicle driveline, is one of the common solutions in the industry. Alternative powertrains typically include turbochargers, fuel cell systems, electric vehicles, hybrid electric vehicles, plug-in electric hybrids, hydraulic hybrids, mechanical hybrids, among others.
Kinetic energy recovery systems (hereinafter abbreviated as KERS), which use a flywheel as an energy storage device, are becoming an important part of hybrid vehicle research. Compared to an alternative such as batteries, which have a great specific energy, flywheels typically store smaller amounts of energy but perform better in terms of specific power. Ultracapacitors and hydraulic accumulators, which also provide strong power characteristics in many hybrid applications, have the disadvantage of being large, heavy, and expensive. Accordingly, flywheel based energy storage device have the advantages of delivering a high amount of power for a relatively small weight, package size, and cost.
Flywheel based energy storage devices are known in the art, and vehicle manufacturers have incorporated such devices in buses, trams, and experimental vehicles. However, as a result of the improvements in the materials used to form flywheels, previous disadvantages such as weight and gyroscopic forces associated with flywheels can be significantly reduced. The use of composite materials such as carbon-fiber polymers, instead of steel, has created a large potential to implement flywheel based energy storage devices in hybrid vehicles.
It would be advantageous to develop a vehicle driveline including a flywheel that improves a fuel economy of a vehicle, permits a size of a power source to be reduced, reduces vehicle emissions, increases a brake life of the vehicle, and reduces maintenance costs associated with the vehicle.